As set out in the material incorporated by reference, the Applicant has developed ink jet printheads that can span a print medium and incorporate up to 84,000 nozzle assemblies. Furthermore, the printheads are able to generate text an images at speeds of from 20 ppm up to 160 ppm, depending on the application.
These printheads includes a number of printhead chips. The printhead chips include micro-electromechanical components, which physically act on ink to eject ink from the printhead chips. In order to achieve the necessary movement, the components incorporate thermal bend actuators. These use differential heat expansion to generate the necessary movement.
It is important to note that the components are microscopic. It follows that heat expansion is far more dramatic than at the macroscopic scale. The components are required to operate at very high speeds in order to achieve the print rate mentioned above. In commercial applications, these high speeds must be maintained for long periods of time. Applicant has found that the printhead chips operate most efficiently at a high heat. However, oscillatory movement at high speed and high heat for extended periods of time can create fatigue damage. This is particularly the case where the components include metal, as is the case with many of the printhead chips developed by the Applicant.
Applicant has found that oxidation tends to occur when the components are operated at temperature, which would otherwise be optimal. Accordingly, the Applicant has conceived the present invention to address the problem of oxidation at the high temperatures. As a result, the Applicant has developed a printer that has printheads that are capable of operating at optimal temperatures while avoiding oxidation.
The overall design of a printer in which this invention is applied is based on the use of replaceable printhead modules. The modules are in an array approximately 8 inches (20 cm) long. An advantage of such a system is the ability to easily remove and replace any defective modules in a printhead array. This eliminates having to scrap an entire printhead if only one chip is defective.
A printhead module in such a printer can be comprised of a “Memjet” chip, being a chip having a vast number of the nozzle assemblies mentioned above. The components, which act on the ink, are can be those as disclosed in U.S. Pat. No. 6,044,646, incorporated by reference. However, other chips may also be suitable.
The printhead might typically have six ink chambers and be capable of printing four-color process (CMYK) as well as infrared ink and fixative.
Each printhead module receives ink via a distribution molding that transfers the ink. Typically, ten modules butt together to form a complete eight-inch printhead assembly suitable for printing A4 paper without the need for scanning movement of the printhead across the paper width.
The printheads themselves are modular, so complete eight-inch printhead arrays can be configured to form printheads of arbitrary width.
Additionally, a second printhead assembly can be mounted on the opposite side of a paper feed path to enable double-sided high-speed printing.